Update IrrigationSchedulerApp.groovy

Added ability to select which rain to add to virtual rain gauge.  For example, you can choose to add yesterday's rainfall, the rainfall today up until the time the sprinkler system starts and/or today's forecasted rain.

I found that during the hot summer, removing the forecasted rain gave a better result, since the rain may (or may not) come until later in the day.  Whereas in the spring, delaying my irrigation if there was forecasted rain appropriately delayed watering.

Now you get to choose!